1. Field of the Invention
The present invention generally relates to the field of communications and the use of wireless handsets. More particularly, the present invention relates to wireless handsets with enhanced functionality, including the ability to operate within a wireless network and in a direct handset-to-handset communication mode.
2. Acronyms
The written description provided herein contains acronyms which refer to, for example, various communication services, components and techniques, as well as features relating to the present invention. Although some of these acronyms are known, use of these acronyms is not strictly standardized in the art. For purposes of the written description herein, acronyms will be defined as follows:                Citizens Band (CB)        Complimentary Metal Oxide Semiconductor (CMOS)        Customer Premise Equipment (CPE)        Electronically Erasable Programmable Read Only Memory (EEPROM)        Federal Communications Commission (FCC)        Group System for Mobile Communications (GSM)        Interim Standard (IS)        Liquid Crystal Display (LCD)        Mobile Identification Number (MIN)        Mobile Switching Center (MSC)        Mobile Telephone Switching Office (MTSO)        Number Assignment Module (NAM)        Personal Access Communication System (PACS)        Personal Communications Network (PCN)        Personal Communications Services (PCS)        Personal Handyphone Systems (PHS)        Public Land Mobile Network (PLMN)        Plain Old Telephone Service (POTS)        Public Switched Telephone Network (PSTN)        Random Access Memory (RAM)        System Access List (SAL)        Supervisory Audio Tone (SAT)        System Identification Code (SID)        Subscriber Identity Module (SIM)        System Operator Code (SOC)        Signal Strength (SS)        Transmission Control Protocol/Internet Protocol (TCP/IP)        Time Division Multiple Access (TDMA)        
3. Background and Material Information
Traditionally, wireless handsets have been provided to facilitate mobile communications. Such handsets are typically assigned a unique wireless or mobile identification number. By dialing the number assigned to the handset, a user may attempt to access a wireless handset user through the wireless network infrastructure. The wireless network may facilitate communications between two mobile wireless handset users, or between a user located at a fixed location (such as, for example, a Plain Old Telephone Service (POTS) station location) and a wireless handset user. In addition, the wireless network may comprise a cellular network or a mobile telephone network to facilitate communication.
Wireless networks enable mobile station users to roam over large geographic areas while maintaining immediate access to communication services. Mobile station users often carry their handsets or have them installed in their vehicle(s). Mobile stations comprising cellular telephones or wireless handsets may be operable in cooperation with cellular or Personal Communications Services (PCS) communications systems. Cellular communication systems typically provide service to a geographic area by dividing the area into many smaller areas or cells. Each cell is serviced by a radio transceiver (i.e., a transmitter-receiver base station or cell site). The cell sites or base stations may be connected to Mobile Telephone Switching Offices (MTSOs) or Mobile Switching Centers (MSCs) through landlines and/or other communication links. The MSCs may, in turn, be connected via landlines to the Public Switched Telephone Network (PSTN).
FIG. 1 illustrates the main components of a conventional cellular network. As shown in FIG. 1, a wireless handset 38 may place or receive calls by communicating with a cell site 30 or a cell site 40, depending upon the location of the wireless handset and the cell coverage area that is provided by each cell site (i.e., cell coverage area 35 of cell site 30 or cell coverage area 45 of cell site 40). For purposes of illustration, wireless handset 38 is depicted in FIG. 1 as being able to communicate with either cell site 30 or cell site 40, even though the wireless handset is not illustrated as being located within cell coverage area 35 or cell coverage area 45. Under normal operating conditions, the extent to which wireless handset 38 will be able to communicate with cell site 30 or cell site 40 will depend on the geographic location of the wireless handset and the size of the cell coverage area of each cell site. Further, although only two cell sites are depicted in FIG. 1, the entire cellular network may include, for example, more than two cell sites. In addition, more than one cell site may be connected to each MSC and more than one wireless handset 38 may be operating within each cell site.
Wireless handset 38 may include a conventional cellular telephone unit with a transceiver and antenna (not shown) to communicate by, for example, radio waves with cell sites 30 and 40. Various air-interface technologies may be implemented to facilitate communication between each wireless handset and the cell sites. Cell sites 30 and 40 may both include a radio transceiver (not shown) and be connected by landlines 16 or other communication links to MSCs 24, 28. A PSTN 12 is also connected to each of the MSCs 24, 28 by landline 16 or other communication links. PSTN 12 may also be connected to fixed Customer Premise Equipment (CPE) 6 (which may include telephone equipment) by communication or trunked lines 10.
The MSCs 24,28 may b e conventional digital telephone exchanges that control the switching between PSTN 12 and the cell sites 30 and 40 to provide wireline-to-mobile, mobile-to-wireline and mobile-to-mobile call connectivity. Each MSC may perform various functions, including: (i) processing mobile station status data received from the cell site controllers; (ii) handling and switching calls between cells; (iii) processing diagnostic information; and (iv) compiling billing information. The transceiver (not shown) of each cell site 30 and 40 provides communications, such as voice and data, with each wireless handset 38 while it is present in its geographic domain. The MSCs 24, 28 may track and switch wireless handset 38 from cell site to cell site, as the wireless handset passes through various coverage areas. When wireless handset 38 passes from one cell to another cell, the MSC of the corresponding cell may perform a “hand-off” that allows the wireless handset to be continuously serviced.
In the current North American cellular system, any given area may be serviced by up to two competing service providers of cellular airtime communication services. By Federal Communications Commission (FCC) regulations, the two competing cellular service providers are assigned different groups of frequencies within the 800-900 MHZ region through which services are provided. A frequency set typically includes control channels and voice channels. The control channels are used for preliminary communications between a mobile station and a cell site for setting up a call, after which a voice channel is assigned for the mobile station's use on that call. The assigned frequency sets are generally referred to as “A band frequencies” and “B band frequencies”. Typically, the A band frequencies are reserved for non-wireline service providers, while the B band frequencies are reserved for wireline service providers. While each frequency set for a given cellular service area is assigned to only one service provider, in different service areas the same frequency set may be assigned to different service providers or companies. Cellular service providers often charge usage fees for airtime since they have to purchase or license the wireless bandwidth over which cellular calls take place, and because they have to maintain their wireless network. The FCC, however, has also designated unlicensed bands in Northern America which do not require a license to operate on if the transmit power is sufficiently low. For example, the 902-928 MHZ Industrial, Scientific and Medical band is unlicensed in the United States. This band is commonly used for home cordless telephones and is well suited for voice communications at limited distances.
Depending upon which cellular service provider is subscribed to by the user of the wireless handset, the home frequency set of the user may correspond to the A frequency band or the B frequency band. Whenever a call is placed by the mobile station or wireless handset, the unit will ordinarily attempt to use the home frequency set to establish the call. If a call is handled outside of the user's home network area, then the unit is said to be “roaming” and service will be attempted through a frequency set of the preferred service provider in that area. Typically, the user's home service provider will have a roaming agreement or reciprocal billing arrangement with the non-home service provider to permit service to be extended to the user's wireless unit when it is roaming in the non-home service provider's service area.
The wireless handset may include a memory device, such as a number assignment module (NAM), in which an assigned phone number (MIN) and a system identification code (SID) is stored to uniquely identify the home service provider for the unit. In addition, the wireless handset may store a unique Electronic Serial Number (ESN) that is assigned to the wireless handset. In the North American cellular system, each cellular market or provider is assigned a distinct, fifteen bit SID. In Europe, on the other hand, the Global System for Mobile Communications (GSM) standard (see, for example, Recommendation GSM 02.11, Service Accessibility, European Telecommunications Standards Institute, 1992) defines a process for network selection based on the wireless handset reading the GSM equivalent of the SID, called the Public Land Mobile Network (PLMN) identity. The SID or equivalent system identification number is broadcast by each service provider or cellular provider and is used by the wireless handset to determine whether or not the wireless handset is operating in its home network or if it is operating in a roaming condition. The wireless handset makes this determination by reading the SID that is broadcast in the cellular market in which it is located, and comparing it to the home SID stored in the NAM of the cellular phone unit. If the SIDs do not match, then the wireless handset is roaming, and the mobile station must attempt to gain service through a non-home service provider. Due to the imposition of a fixed surcharge or higher per unit rate, the airtime charges when the mobile station is roaming are customarily higher than when it is operating within its home network.
When a wireless handset is switched ON, the handset scans the group of control channels to determine the strongest cell site or base station signal. Control channels are primarily involved in setting up a call and moving it to an unused voice channel. When a telephone call is placed, a signal is sent to the cell site or base station. The MSC usually dispatches the request to all base stations in the cellular system. The MIN which is assigned as the phone number to the wireless handset is then broadcast as a paging message throughout the cellular system. When the wireless handset receives the page, the handset identifies itself to the base station it received the page from (usually the strongest base station) and informs the MSC of the “handshake”. The MSC then instructs the base station to move the call to an unused channel. As noted above, the MSC may also provide access to the PSTN once a channel is established.
Operation under a roaming condition is often under the control of the wireless handset user. The user can select whether the mobile station will operate in a Home System Only, A Band Only, B Band Only, A Band Preferred, or B Band Preferred operating mode. The user typically controls the system preference and mode operation through menu choice or selection. This current method of roaming control is conventionally known as “Preferred System Selection”. In the most common roaming situation, the wireless handset remains on the same band as the home cellular network. That is, if the wireless handset is homed to a cellular network with an odd numbered SID (which is normally assigned to an A band cellular service provider), then the wireless handset will obtain service from the A band cellular service provider when roaming.
In addition to conventional cellular network systems, Personal Communications Services (PCS) systems are also available. PCS covers a broad range of individualized communication services. However, providing cellular or PCS services is costly. To recover these costs, a subscriber is normally required to pay a monthly fee and additional fees may be charged for time spent talking on the wireless handset (often referred to as airtime). Some service plans may give a subscriber a certain number of minutes of airtime free per month and then charge for every minute over that allotment. Other plans may charge for every minute spent using the wireless handset. In addition, the subscriber is often required to purchase the wireless handset or sign a multi-year service contract. Additional charges may also be incurred for service features (such as voice mail) or using the wireless handset in other service markets. Roaming charges can be costly, especially where preferred roaming carriers are not available.
Forms of wireless or mobile communication that do not incur these fees are also available. For example, cordless phone systems, land mobile radio systems, CB radios and walkie-talkies are available. Cordless phone technologies are often utilized in home or office environments and operate over unlicensed bands to provide wireless or cordless phone capabilities via a cordless phone base station. Cordless phone units typically employ a manufacturer's proprietary protocol to manage full duplex communications between the handset and a single cordless phone base station connected to a phone line. Further, land mobile radio systems, CB radios, walkie-talkies and radios using the new family band provide half duplex (push-to-talk) wireless voice comminations over extended ranges (e.g., at ranges up to 2 miles). These devices communicate directly by broadcasting voice signals over channels that are shared with anyone who buys a similar device and desires to listen in to the conversation.
Such technologies do not incur fees, since they do not rely upon a wireless network infrastructure or service provider, such as with cellular or PCS units. However, these devices also suffer from several drawbacks. For example, cordless phone systems operate over limited ranges and do not support direct handset-to-handset communication, since all calls are handled through the cordless phone base station. Cordless phone units also have limited capabilities and operating features that restrict their usefulness. Further, while land mobile radio systems, CB radios, walkie-talkies and other radio systems provide direct communication between units over extended ranges, such devices do not provide any level of privacy since all signals are broadcasted by the units and may be received by other parties. In addition, radio devices only provide half-duplex communications and require that users manually select similar operating channels.
In recent years, Personal Handyphone System (PHS) handsets have been provided as an alternative and more economical solution for wireless communications. PHS systems utilize low powered handsets and a micro-cell network architecture including a large number of cell stations to provide coverage. Each cell station picks up a carrier at random from those available and selects a carrier on the basis of least interference. A traffic channel is then allocated to provide wireless communications. PHS systems also provide other features, such as user authentication, location registration and seamless handover during calls. PHS systems, however, have not been commercially successful in many developed countries (including the United States and Germany) and have limited handset features.
In view of the foregoing, there is presently a need for a full-featured wireless handset that includes enhanced features or capabilities to provide a user with greater flexibility and optimum performance. For example, many users would benefit from a full-featured wireless handset that is capable of operating within a wireless network (such as a cellular phone, PCS or PHS network), as well as operating in a direct handset-to-handset mode within a limited range but without the utilization of a wireless network. Since direct handset-to-handset calls avoid the use of a wireless network, users would be provided with the benefit of being able to place calls free of the wireless network and with little or no airtime charges (i.e., monthly service or use charges could be applied to the user by the supplier of the wireless handset). A full-featured wireless handset with such functionality would have broad appeal to many users and could be applied to many applications to permit users to reduce their cellular phone charges. There is also a need for an improved wireless handset that has enhanced features, and which does not suffer from the drawbacks of existing communication devices, such as those described herein. For example, a wireless handset that is capable of operating in a direct handset-to-handset communication mode would be beneficial if it included enhanced features, such as full-duplex, private communication, dynamic channel allocation and handset locating capabilities. Such features would eliminate the need for users to prearrange or manually select operating channels (which is a common drawback in radio systems such as CB radios) and provide full duplex communication free of a communication network and without incurring substantial airtime charges.
Various user groups and industries would benefit from such an enhanced wireless handset. For example, the functionality of such a wireless handset is currently needed by mobile crews, on-site mobile personnel, businesses, teachers, teenagers and families. Mobile crew workers, including contractors, electricians, plumbers, tow truck drivers and caterers, have a strong need for such a wireless handset to enable such personnel to keep in contact with one another at various job sites and to facilitate collaboration on projects at a substantial cost savings. On-site mobile personnel, such office building employees and personnel, security personnel, and warehouses, as well as teachers and other faculty members would also benefit from such a wireless handset, by enabling them to keep contact with other personnel and departments while spending much of their day in transit or in remote locations of the job site. In addition, there is a need for an enhanced, wireless handset communication device by teenagers and families which wish to keep in contact with one another during social events or vacations. Such a device would also provide an inexpensive solution for locating one another and preventing parties from being lost or separated.